to the same thing, twohoxes and the foundry floor), and make the
flange A loose on the pattern. On taking off the top box, this
flange maybe withdrawn, while on replacing the top box, and lifting
it and the bottom box together, the main pattern may then be
removed. The core for the centre is inserted in the usual way,
and the casting made in the position shown. The stakes s s fix the
position of the boxes with regard to the floor. (See App.II.,p. 781.)
v Casting" on.—Sometimes it is necessary to attach cast iron
to wrought iron in the mould itself, and so do away with the
expense of bolts. Casting on is the term adopted for the opera-
tion resorted to.
As an example, we will take the traction engine Road
"Wheel, shown in section, Fig. 17.
A core box is made as in Fig. 18, consisting of a slab of
wood A, with the boss B fastened to it, and of a hollow cylinder
of wood c to contain the core sand. Two cores are thus formed
and baked in the stove. A second core box is required, shown
in Fig. 19, consisting, as before, of a hollow box to hold the core,
and of the bosses DD in two parts, to make the impression for
the central part of the wheel nave. As the line oc in Jig. 18
corresponds to line x on Fig. 19, it will be seen that the prints
ppin Fig. 18 will leave spaces for the reception of the spokes.
It is only necessary to fix the spokes loosely in place by bolts to
wheel-rim, at the same time laying them in the spaces left for them
in the cores; build up according to
Fig. 20; add a central core, E, made
in ordinary core box; make gates, and
cast. The spokes are afterwards
riveted on wheel rim, and have the shape shewn in Fig. 21.